Multicore oil-filled high tension electric cable



Oct. 18, 1932. 1 EMANUEU 1,883,648

MULTICORE OIL FILLED HIGH TENSION ELECTRIC CABLE Filed July l2, 1929 Patented Oct. 18, 1932 UNITED STATES PATENT .OFFICE LUIGI EMANUELI, or MILAN, ITALY, AssIGNon To SOCIETA ITALIANA PIILELLI, or

MILAN, ITALY MLTICORE OIL-FILLED HIGH TENSION'ELECTRIC CABLE.

Application filed July 12, 1929, Serial No. 377,851, and i'n Italy J'uly 9, 1928.

The present application. is a continuation inppart of my prior application Serial No. 328,655 filed December 27, 1928. f

This invention relates to multicore high ltension electric cables having internal longitudinal channels filled with oil or Afluid insulating compound for the purpose of'permanently feeding the impregnated insulation of the cable, the channels being placed in communication at predetermined distances along the ciable, for example at the terminals or at some of the joints, withf feedingV tanks or reservoirs containing oil or fiuid insulating compound.

Y reduces the dielectric strength of the cable to a lower value, because the oil, which has a lower dielectric strength than that of the impregnated' insulation, is located in the ,Y weakest points of the cable, that is in the points adjacent to those of the mutual contact of the cores.

The present invention'has'or its object to provide a multicore cable in which even though the cavities for the oil are located in the spaces between the cores, a high dielectric strength is maintained in the points adjacent to those of the mutual contact of the cores.

For this purpose, according tothe present invention a mult-icore high tension electric cable, wherein channels, which are filled with oil or fiuid insulating compound, are located in the spaces between the cores and the sheath, is characterized in that small internal fillings, made of material permeable to oil, are provided in the spaces enclosed between the walls of the channels and the cores and defined by the points of contact with one another of two cores and the walls of a channel or of one core and the walls of two channels.

In the case for example of one construction of three cores cable in accordance with the invention, there would be a central filling occupying the centr-al space between the three' i cores, and three internal fillings, each such latter filling being-closely wedged in the- 4fillings the lead sheath of the cablelis placed,

with or without the interposition of the usual external insulatedY belt. A

The spaces inside the tubular channels serve tocontain the oil or fluid insulating compound, channels with permeable Walls feeding the cable through which they pass, whilst channels with impermeable walls serve to carry oil to some distant part of the cable without loss on the way. A

In order that the invention may be clearly understood and readily carried into effect, the same will now be described more fully with reference to the accompanying drawing, in whichz- Figure 1 illustrates in section one construction of three phase cable in accordance with the present invention.

Figure 2 is a section view of another construction of three phase cable according to the invention. Y

Figure 3 illustrates a tubular channel with impermeable walls.

Figures 4 to 8 inclusive illustra-te various types of the tubular channels with permeable walls, and

Figures 9 to 10 inclusive illustrate various foilms of cross-section of the tubular channe s.

lIn the construction of cablesillustrated in Figures 1 land 2 there are shown the conductors 1, the insulation 2, the lead sheath 3, the central filling 4, and internal fillings '5, the walls 6 of the tubular channels, the

tubular channels 7 (Figure. l) or 7 and 7a (Figure 2) and the vkperipheral fillings Over thcores,

`The Walls of' the tubular channels can be and the smaller channels 7 with permeable walls, or vice versa. When they are made permeable to the oil the walls of theV channels can have the form of a meshed tube, (as

shown in Figure 4), or a thin walled tube with small perforations or holes'therein (see Figure 5)". or with cuts or slits as shown in Figure 6, or they may have the formof a short lay Awire helix k(see Figuref), or tape helix (see Figure 8), the tape having the' edges rounded towards the inside of the helix.

The cross section of the tubular channels may be circular as shown in Figure 1, or e1- liptical as shownn in Figure 9, or of any other form which conforms with the bounding surfaces of the cores and lead sheath as/illnstrated for example in Figure 10, the dimensions of the internal and peripheral fillings being, of course, determined by the section of the tubular channels.

' When the walls of the channels are formed y of electrically conductive material it may be convenient, in some cases, that the internal fillings also be made of electrically conductive A material for example a filler, of paper contain-y ing' in suspension metallic powder, or a paper filler covered with metallized paper, or a substance consisting of condudcting'materials reduced to thefinest powder; these may, moreover, be in electrical communication with the lead sheath, for instance, in the joints between the various lengths of cable, in which case the electric field in each core does not diiler very much from the perfectly radial one of single core cable.

To prevent the lead sheath from expanding or bulging due to the pressure of the oil within the cable, it may be advisable in many cases toy wrap the lead sheath with a thin metal tape 13. This tape or ribbon may alsofbe made of iron or other magnetic metal, as the power losses thus introduced in a multicore cable are still admissible. To vprevent the tape and particularly the edges thereof from cutting into the lead sheath 3 a few layers of suitable material such as paper 14 are interf posed between the two. An outer lead sheath 15 surrounds the cable thus formed and protects the metal tape from chemical action -of external agents.`

The improvedtype of multicore cable according to the present invention described above has all the advantages of all cables with oil-feeding channels in the spaces between the cores, that is it has a section suilciently large to render easy the feeding of oil without increasing the diameter of the cable,whilst at the same time however it has not the disadvantages of the known types previously mentioned in which latter the oil occupies entirely the spaces adjacent to the points of mutual contact -of the cores, thus lowering sensibly the dielectric strength of the cable. No claims are made herein based solely on the provisionl of a cable having longitudinal channels the walls of one or more of which are ermeable to the fluid insulating compoun as this subject matter is contained in a prior co-pendingapplication filed by me.

Having now particularly'described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I clain is 1. In a multicore high tension cable, the' combination of conductors, a covering of permeable insulation for each conductor, an outer covering therefor, ,channels for conveying fluid which are located in the spaces between the insulation on the conductors and said covering, some of said channels being permeable to fluid and feeding it directly to the insulation on the conductors, the remainder being impermeable to fluid for conveyin it from one point to a distant part of the oeil-ile, and fillers which are permeable to the fluid and which are held in a compressed state` between the walls of the channels, the insulation on the conductors andthe outer covering. f-

2. In a of three conductors which are bound together, a covering of insulation for each conductor through whichiiuid is free to pass into and from the said insulation, apermeable filler body located in the central region between the conductor insulations, an outer covering for the said conductors, afluid carrying) channel located in each of the spaces defined y the insulation onthe conductors and the inner wall of the covering, some of said channels being permeable to fluid and feeding it directly to and receiving it from the conductor insulations, and the remainderbeing impermeableto uid for conveying it from one point to a distant part of the cable, and permeable lillers which are wedged into the spaces immediately adjacent the channels.

3. In a high tension cable, the combination of conductors arranged about a common cena ter, a covering of permeable insulation for each conductor, an outer metal sheath for the conductors, metal walled channels mwhich are located in the spaces between the insulation on the conductors and are in contact with the in ner wall of the sheath, some of said channels bemg permeable to fluid and feeding it directly tothe insulation on the conductors,-

the remainder being impermeable to the fluid for 'conveying 1t from one point to a distant part ofthe cable, and fillers which are made high tension cable, the combination I" in sa n of the spaces defined between the permeable insulation of adjacentA conductors and the enclosing sheath, some of said channels being permeable-to fluid and conveying the same to the insulation upon the conductors, and some.

of said channels being impermeable to fluid for conveying it from one point to a distant part of said. cable, and permeable fillings in the remaining spaces defined within said enclosing sheat 5. In a multicore, high tension, oil filled electric cable, a plurality of conductors, a covering of permeable insulation for each of said conductors, an impervious -sheath enclosing said insulated conductors, a plurality of channels for conveying fluid within each of the spaces defined between the permeable insulation of adjacent conductors and the enclosing sheath, some of said channels being permeable to fluid `and conveying the same 3' tothe insulationupon the conductors, and

some of said channels being impermeable to fluid for conveying it from one point to a distant part of said cable, and permeable fillings in the remaining spaces defined within said 35 enclosing sheath, a metallic reenforcing tape encircling said sheath, an encircling tape interposed between said sheath and said metallic tape and an outer wear resisting sheath ,covering said metallic tape.

6. In a multicore, high tension, oil filled electric cable, a plurality of conductors, a covering of permeable insulation for each of said conductors, an impervious lead sheath enclosing said insulated conductors, a plu- `45 rality of channels for conveying fluid within each of the spaces defined between the permeable insulation o'fvadj acent conductors and the enclosing sheath, some of said channels l@being permeablel to fluid and conveying the l50 'same to the insulation upon the conductors,

and some of said .channels being impermeable 'to fluid for conveying'it from one point to a distant part of said cable, and permeable filling in the remaining spaces defined withi enclosing sheath, a metallic reenforcing tape encircling said sheath, an encircling paper tapeV interposed between said sheath and said metallic tape and an outer lead sheath-covering said metallic tape.

7 In a multicore high tension cable, the combination of conductors, a covering of permeable insulation for each conductor, an outer cover-ing therefor, channels for -conveying'fluid which are located in the spaces ,65 -between the insulation on the conductors and said covering, some of said channels being permeable to fluid and feeding it directly to 4the insulation on the conductors, the remainder being impermeable to fluid for conveying it from one point to a distant part of the cable, said permeable channels comprising a thin metal ribbon wound flatwise to form a helix, and fillers which are permeable to the fluid and which are held ina compressed state between the walls of the channels, the insulation on the conductors and the outer covering.

8. In a multicore high tension cable, the combination of conductors, a Covering of permeable insulation for each conductor, an outer covering therefor, channels for conveying fluid which are located in the spaces between the insulation on the conductors and said covering, some of said channels being permeable to fluid and feeding it directly to the insulation on the conductors, the remainder being impermeable to fluid for con.

veying it from one point to a distant part of the cable, and electrically conductive fillers which are permeable to the fluid and which are held in a compressed state between the walls of the channels, the insulation on the conductors and the outer covering. c

9. In a multicore, high tension, oil filled electric cable, a pluralityof conductors, a

covering of permeable insulation for each ofI trically conductive permeable fillings in the remaining spaces defined within said enclosing sheath. I

10. In a multicore, high tension, oil lled electric cable, a plurality of'conductors, a covering of permeable insulation for each of said conductors, an impervious shea-th enclosing said insulated conductors, a plurality of channels for conveying fluid within each of the spaces defined between the permeable insulation of adjacent conductors and the enclosing sheathmsome of said chan'- nels being permeable to fluid and conveying the same to the insulation upon the conductors, and some of said channels being imperlmeable to fluid for conveying it from one point to a distant part of said cable, said permeable channels lcomprising a thin metal ribbon wound flatwise to form a helix, and permeable fillings in the remaining spaces defined within said enclosing sheath. 11. In a multicore, high tension, oil filled electric cable, a plurality of'con'ductors, a covering of permeable insulation foreach of said conductors, an impervious sheath enclosing said insulated conductors, a/plurality of channels forconveying fluid within each of the spaces defined between the permeable insulation' of adjacent conductors and theenclosing sheath, some of said channels being permeable.V to fluid and conveying the same to the insulation upon the conductors, and some of said channels being impermeable to Huid for conveying itA from one point to a distant part of said cable, said peraneable channels comprising a thin metal ribbon Wound fiatwise to formahelix, and electrically conductive permeable illings in the remaining spaces deiined within said enclosing sheath.

LUIGI EMANUELI. 

